The present invention relates to power management in electronic devices. More particularly, it relates to remote power management in a downhole device connected to a downhole network.
In downhole operations such as drilling for oil, gas, and water, it is often very desirable to take and record measurements at selected points along a tool string and relay that information to surface equipment. U.S. Pat. No. 6,670,880 to Hall (hereafter referenced as the '880 patent), which is herein incorporated by reference for all that it teaches, discloses a downhole data transmission system which enables one or more downhole devices situated along a tool string to be connected through a downhole network to surface equipment.
One challenge in operating electronic devices in a downhole environment is that of providing them with electrical power. It is often difficult to supply downhole power from the surface of a drilling site, and as a result downhole electronic devices are often powered by special batteries. Batteries have a finite duration of operable utility, and a downhole battery may need to be replaced during drilling operations. In many cases, sensitive electronic equipment is placed in a sealed housing inside of a tool string component in order to protect it from downhole conditions. Under such circumstances, it is inconvenient to remove the sealed portion of the housing to access the equipment installed in the tool string component on a very frequent basis. Also, electronic equipment so housed may be extremely difficult to turn on and off once the tool string is downhole.
In addition to the difficulties in accessing them, another problem arises in the fact that electronic devices on a tool string may be left downhole for considerable amounts of time, thus draining power from the batteries.
Various attempts to maximize power efficiency in electronic apparatus have been made in the drilling industry. U.S. Pat. No. 4,709,234 to Forehand, which is incorporated herein by reference for all that it teaches, discloses a power-conserving apparatus that includes a plurality of independently energizable electrical circuits used in receiving electrical signals from a transducer which senses an environmental condition, in processing the electrical signals, and in storing information related to the detected environmental condition. The apparatus is self-monitoring, and may switch power between the independently energizable electrical circuits.
U.S. Pat. No. 5,960,883 to Tubel, which is incorporated herein by reference for all that it teaches, discloses a method of managing power in a control system in a production well, the control system including a plurality of downhole modules which require power and are addressable. The downhole modules are permanently deployed and are for controlling devices that are operatively associated with them. The method includes the steps of maintaining each module in a dormant, low-power state until activation is required and selectively activating one or more of the modules when activation is required.
U.S. Pat. No. 5,784,004 to Esfahami, which is incorporated herein by reference for all that it teaches, discloses an apparatus with a temperature sensor, a pressure sensor, and a control module. Energy is conserved by sending change-in temperature and change-in pressure data. The control module stores previous measurements, determines a “change-in” calculation, generates transmitter activation signals, and generates a control signal. The control module can go into a sleep mode, and is equipped with a wake-up delay generated by a counter.
U.S. patent application Ser. No. 10/710,638, filed in the name of David Hall on Jul. 27, 2004, and incorporated herein by reference for all that it teaches, discloses that a tool may receive power directly through the tool string; when the source of power is disconnected (e.g. during tripping operations), it may automatically go into a sleep mode powered by a small battery until reawakened by the reinstatement of tool string power.